<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
  <style>
    .test div{
      height: 50px;
      float: left;
    }
    .test>div:nth-child(1){
      background-color: red;
    }
    .test>div:nth-child(2){
      background-color: green;
    }
    .test>div:nth-child(3){
      background-color: blue;
    }
  </style>

  <link rel="stylesheet" href="./01index.css" media="(min-device-width: 200px) and (max-device-width: 600px)">
  <link rel="stylesheet" href="./02index.css" media="(min-device-width: 601px) and (max-device-width: 900px)">
  <link rel="stylesheet" href="./03index.css" media="(min-device-width: 900px) and (max-device-width: 1300px)">
</head>
<body>
  <div class="test">
    <div></div>
    <div></div>
    <div></div>
  </div>
</body>
</html>
